Multiple expansion rotary drill bit



g- 1953 A. w. KAMMERER 2,650,072

MULTIPLE EXPANSION ROTARY DRILL BIT Filed Aug. 18, 1950 2 Sheets-Sheet l 2g INVENTOR.

' 10a Alec/r52 WKA MERE-g 10a 10 BY 27 1 27 ,29 w 29 WW I fir ave-x A. W. KAMMERER MULTIPLE EXPANSION ROTARY DRILL BIT Aug. 25, 1953 2 Sheets-Sheet 2 Filed Aug. 18, 1950 ARCHER WK4MME2E2,

44 ae/vEY- of the kelly of hexagonal shape (Fig. 6), fitting within a corresponding hexagonal socket IT in the body. The drill stem member is provided with an external flange 18 fitting within the body, and serving the purpose of holding the drill stem member within the body. After the drill stem member I3 has been placed into the upper end of the body ii, a retainer ring It may be disposed over the member above its flange [8 and secured to the upper end of the body, as by use or" welding material 20, in order to prevent upward withdrawal of the kelly l3 from the body II.

The body has a plurality of depending leg portions Ila defining longitudinal transverse body slots 2!, in which cutter supporting members 22, 22a, 22?) are disposed. These cutter supporting members are preferably equi-angularly spaced around the bit axis and have their upper ends mounted on pivot or hinge pins 23 extending across the body slots 2| and suitably secured to the body, as by the use of welding material 24. The cutter supporting legs 22, 22a, 22b depend from their hinge pins 23 to a substantial extent. They each have a bearing supporting pin 25 at the lower end, on which a roller side cutter Ill, ita or Nib is rotatably mounted. Anti-friction roller and ball bearing elements 25, 2? are disposed between each bearing supporting pin 25 and cutter it, lea or iflb,

to reduce the friction therebetween. The ball bearing elements 2'? also serve to retain the cutter on the bearing supporting pin.

The balls 2'! may be inserted between each cutter Ill, Illa or lb and its associated pin 25 through a passage 28 in the latter, which is closed by a suitable plug 29 welded, or otherwise suitably secured, to the pin.

The bearing supporting members 22, 22a, 22b, and their cutters it, a, 5213, may occupy retracted positions substantially entirely within the confines of the main bit body I i, or they may be expanded outwardly of the body to a larger effective diameter than the inside diameter of a casing string (not shown) through which the bit is moved, for the purpose of enlarging the well bore below the casing shoe (not shown). In expanding the cutters ill, illa, 18b, their supporting legs 22, 22a, 222) are swung outwardly about the hinge pins 23 to a predetermined extent.

The device for holding the cutters expanded includes a lower tubular member 3!}, which actually forms part of the mandrel l2, and which is piloted within a lower socket Si in the kelly l3. The kelly 53 and lower tubular member 35 are assembled together for joint longitudinal movement by a swivel connection 32, which enables the lower tubular member to move angularly with respect to the upper kelly. Such swivel connection may include ball bearing elements 33 mounted in a raceway 34 formed on an enlarged portion 35 of the lower member 30, the ball bearing elements also being rollable in an internal raceway 35 formed in the kelly itself. The balls may be inserted in place through a passage 31 extending through the Kelly flange l8. After the required number of balls have been mounted in the raceways 34, 36, they are held in assembled position by a plug 38 in the passageway 31, which is prevented from inadvertent outward movement from the passageway by engaging the main bit body l l.

The lower tubular member 32 depends from its boss portion 35 through a guide and thrust member 39, which rests upon a shoulder 40 formed on the body. This thrust member initially is disposed below the lower end of the kelly 43, so as to allow the kelly 13 and tubular member 39 to be moved downwardly, for the purpose of holding the cutters i2, Illa, ii and their supporting members 22, 22a, 22b in an outward position, resisting inward movement of the cutters from their outward position, and, under some conditions, actually shifting the cutters to their outwardly expanded position. The lower end of the mandrel member 32 is slidable in a lower guide 4! integral with the body II, and forming a support for the mandrel to resist its lateral movement.

The cutter supporting members or legs 22, 22a, 22b and the cutters may be expanded outwardly by a compressed helical expander spring 52 encompassing the tubular member 30 and bearing upon an upper seat or shoulder 51 formed in the main body of the bit. The lower end of the spring bears upon an upper thrust block 52, that has a pin 55 carrying the upper end of a link or connecting rod 54, whose lower end is pivotally mounted on a pin 55 suitably secured to the cutter supporting leg 22.

Slidable on the mandrel 30 below the upper thrust block 52 is an intermediate thrust block 52a having a pin 53a on which the upper end of a thrust link or connecting rod 54a is pivoted, the lower end of this link being pivoted on a pin 55a secured to another one of the cutter supporting members or legs 22a. Yet another or lower thrust block 5212 is slidable on the mandrel below the intermediate thrust block 52a and carries the pin 531) on which the upper end of a lowermost link 54b is pivotally mounted, the lower end of this link being pivoted on a pin 55b secured to still a third cutter supporting member or leg 22b.

As illustrated, the upper, intermediate and lower thrust blocks 52, 52a, 522) are slidable on a reduced diameter lower portion 30a of the tubular member 35, the upper thrust block 52 being initially disposed adjacent a mandrel shoulder 301), which may engage the upper portion of the upper thrust block.

One manner of expanding the cutters outwardly is to allow the compressed spring 52 to expand, which will shift the upper thrust block 52 downwardly on the mandrel 30, and, through the agency of the link 54, urge the cutter supporting leg 22 and the cutter l0 outwardly. The upper thrust block 52 will move downwardly under the influence of the spring 50 until it engages the intermediate thrust block 52a, the spring then moving both the upper and intermediate blocks 52, 52a downwardly as a unit to urge the cutter supporting legs 22 and 22a outwardly. Thereafter, as the spring 5!] continues to expand, the intermediate thrust block 5211 engages the lower thrust block 52b, the three blocks 52, 52a, 52b moving downwardly as a unit to urge all three of the cutter supporting legs 22, 22a, 22b and their associated cutters l0, Na and [0b outwardly, through the agency of the intermediate connecting rods 54, 54a, 54b. The extent of expansion is limited by engagement of the lower thrust block 521) with the lower body guide 4!.

The spring 50 can be efiective to urge the cutters outwardly in the event it is desired to begin enlarging the well bore below the well casing at a point above the bottom of the hole. If desired, the tubular mandrel 35 can be employed, in the absence of the expander spring 50, or to supplemer t the expander s ring, in urging the cutters m, we, fob outwardly, particularly if downward movement or the body II can be prevented or resisted by thebottom of the weli bore, as upon resting of a pilot bit E on the bottom. It is to be noted that the driving mandrel l2 originally occupies an upper position with respect to the body Ii. Down-ward movement of the mandrel by urging the drill pipe string B downwardly will force the mandrel shoulder 30b against the upper thrust block 52 and first urge the cutter supporting leg 22' and its cutter l outwardly. As downward movement of the mandrel l2 within the body H continues, the upper thrust block engages the intermediate block 520 to urge the secondcutter supporting leg zzoand cutter I-iia outwardly. Continued downward movement will then caus the intermediate block to engage the lowermost block 526, for the urpose of urging the third cutter supporting leg 22b and cutter Illb' outwardly. The extent of such urging will be determined by engagement of the lower end [3a of the kelly 13 with the upper thrust and guide washer 39.

The cutters In, [0d, lOb ma be locked in retracted position initially by" a holding device, with the expander spring 50 fully compressed, and with the drivingmandrel i2 occupying an upward position within the body ll; so as to insure downward passage of the bit through the well c'asin'g, and to enable the bit to be moved to any desired point in the well bore below the casing shoe before the hole enlarging operation is commenced. This holding device may include aholding plate 60' having holes 61 receiving the lower ends of the bail retaining plugs 29. The plate 69 will prevent outward expansion of the cuters' until th former member is removed. Such re-inov'al may be effected hydraulically. Thus, a central rod 62' is secured to the plate and projects upwardly into the central passage 30o formed through the lower tubular member 30. A head 63 at the upper end of the rod fits loosely within the passage sec", to enable fluid to new upwardly through the tubular member passage and the lr'elly assage I 3b and into the drill pipe string B. A ball 64 may also be disposed in the passage see, or may be dropped down the drill pipe B when the cutters are to be expanded, this ball having a diameter substantially equal to the diameter of the passage 360; so as to function as a piston and enable the fluid under pressure within the drill pipe B and drill bit to force the central rod is; downwardly and remove the holding plate Ell from the plug elements 29, whereupon the cutters HI, lea, illb and their supporting members 22, 22a, 221) can be shifted laterally outward, either by the expander spring 59, the driving mandrel W, or both.

It is desired to have each of the cutter mem-- bers operate upon a particular annular portion of the formation shoulder. Thus, the cutter mem-' ber Ii} is to operate around the annular portion R of the shoulder. (see Fig. the cutter memher I to is to operate upon the annular portion S of the shoulder; and thecutter member it?) is to operate upon the annular portion T of the shoulder. Inasmuch as these annular portions are disposed different lateral distances from the axis of the well bore, the cutters are to be expanded outwardly different amounts to locate each cutter at its proper position upon the for mation shoulder C.

Since the cutter supporting leg 22 and its cutt'er It are to be swung outwardly from their 6 fully retracted psififi t6 the greatest extent, the pin connection 55 between the connecting rod 54 and the cutter supp rting leg 22 is disposed a lesser distance from the hinge pin 23 of the cutter supporting leg' 22, than the distance from its hinge pin of the pin connection 55a between the second cutter supporting leg" 22a and its connecting rod 54c. Similarly, the distance from the hinge pin '23 for the cutter supporting leg 22!) and its pin connection 55b with its connecting" rod 54b is greater than the distance between the hinge pin of the second leg 22a and its pin connection 55a to its link or connecting rod 54a. Accordingly, for the same longitudinal movemerit, the upper thrust block 52' will swing its outter supporting leg a greater arcuate extent than the intermediate thrust block 52a will swin it cutter supporting leg 22 a, and this latter thrust block will, in turn, swing the cutter suporting leg 22 a greater arcuate distance than the lower thrust block 5217 swings the cutter suporting leg 22o; V

Despite thefact that the lever arm distance of the pins 55, 55a, 55b connecting the rods 54, 5411, I

541) to the cutter supporting members is different, it is desired to have the first cutter supporting leg 22 swing outwardly to a certain arcuate extent before the intermediate supporting leg 22a commences moving outwardly from its retracted position. Also, this intermediate leg 22a is to swing outwardly from its fully retracted position to a certain extent before the remaining leg 2% and its cutter illb commences moving outwardly. To accomplish this purpose, the intermediate thrust block 52a is initially spaced downwardly from the upper thrust block by a certain distance; so that the upper thrust block 52 must move downwarolly through this distance and swing its cutter supporting leg 22 and cutter Ill outwardly before the upper thrust block 52 engages the intermediate thrust block 52a, to commence outward swinging ofthe intermediateleg 22a and cutter Ina. Similarly, a longitudinal space exists initially between the intermediate and lower thrust blocks 52a, 52b, to require the intermediate thrust block 52:; to swing the intermediate cutter i no outwardlylto a certain arcuate extent before it engages the lower thrust block 521) and shifts the latter downwardly, to effect outward swinging' of the cutter supporting leg 22b and cutter lob; y g

Thus, the upper thrust block 52 will move downwardly to shift the cutter HJ outwardly, and while the drill string and bit is rotating, cause the cutter to start producing the formation shoulder C. After the inner portion T of this formation shoulder is formed by the outward expansion of the cutter Hi, the upper thrust block 52 will then engage the intermediate thrust block 52a and commence shifting the intermediate cutter Illa" outwardly. The first cutter Iii has been expanded outwardly to a greater extent than the second cutter Mia and will remain in this advanced position during rotation of the drill bit, whereby-the first cutter I'll enlarges the formati'on' shoulder C to a still greater lateral extent as by commencing to operate upon the formation shoulder portion S. The second cutter Illa, duringfurther outward swinging of the first cutter l8, will be disposedover the inner portion T of the formation shoulder. As the two thrust blocks 52, 52d rno'ife" downwardly as a unit along the mane-roles, to expand their cutters H), Illa. out- I waremthe' intermediate block engages the lower thrustblock 5 211 and commences urging the remaining cutter supporting leg 22b and cutter Hlb outwardly. Inasmuch as all three thrust blocks are contacting one another, they will swing outwardly simultaneously, the first supporting member 22 and its cutter Ill leading the second supporting member 2201, and its cutter Illa in lateral extent, and the second cutter supporting member and its cutter, in turn, leading the remaining supporting member 2217 and its cutter Iflb in lateral extent. The blocks all continue moving downwardly to their maximum extent, the first cutter I swinging across and producing the entire formation shoulder C, and finally being capable of rolling around the outermost annular portion R of the shoulder. The second cutter [0a is capable of rolling around the intermediate annular portion S of the shoulder, and the third cutter Illb is capable of rolling around the inner annular portion T of the shoulder.

In the event that the thrust blocks have been shifted downwardly by the spring 50, the production of the full shoulder C will enable the operator to lower the drill pipe B slightly, to telescope the mandrel I2 within the body II until the lower end I3a of the kelly I3 engages the thrust washer I311. The drilling weight can then be imposed directly through the kelly I3 onto the body I I, and through the hinge pins 23 and supporting members 22, 22a, 22b to the cutters I0, [0a, Illb. At the same time, the mandrel shoulder 30!) is disposed immediately adjacent the upper thrust block 52, in order to hold all of the thrust blocks in their downward position and preclude the reactive forces of the formation on the cutters from urging the latter inwardly to a position in which they would drill an undersized hole. In effect, the mandrel shoulder 30b looks or retains the cutters outwardly to their maximum expanded positions.

The tool A is assembled with the parts occupying the positions illustrated in Fig. 3, the holding plate 60 securing the cutters I0, a, 10b in retracted position, with the spring 50 (when a spring is used) under maximum compression. The tubular mandrel I2 is disposed upwardly with respect to the body I I, as limited by engagement of the Kelly flange [B with the retainer ring I9. The bit is attached to the drill pipe B and lowered in the well bore.

When the location in the bore hole below the casing shoe has been reached at which the underreaming or hole enlarging operation is to commence, the pumps at the top of the well bore are started and the fluid in the drill pipe B subjected to pressure. This pressure acts upon the ball 64 and forces both the ball and the central rod 62 out of the passage 390, which removes the holding plate 60 from the plug elements 29 and allows the entire holding device to be ejected from the bit, leaving the passage 300 free and allowing the circulating fluid to exit from the lower end of the passage into the well bore, for the purpose of cleaning the cutters and washing the cuttings upwardly to the top of the well bore.

After the holding device has been removed, the spring 50 can expand. This expanding action first urges the upper block 52 downwardly, and, through the thrust link 54, swings the first cutter IE! outwardly, forcing the cutter I0 against the wall of the formation. The drill pipe and the rotary drill bit are then rotated at the proper speed, without imposing drilling weight on the pipe and bit, the single cutter I0 digging into the wall of the formation and commencing the production of the inner portion T of the shoulder C therein under the influence of the spring 50. As the spring expands, as a result of outward movement of the first cutter II], the upper block 52 moves down until it engages the intermediate thrust block 52a, which then urges the second cutter supporting member 22a and cutter Illa outwardly. The spring 50 continues its expansion, simultaneously shifting the first and second cutter supporting members 22, 22a and their associated cutters 10, [0a outwardly, the first cutter l0 leading the second cutter Illa and continuing to enlarge the lateral extent of the formation shoulder, commencing the production of the intermediate portion S of the shoulder during rotation of the drill bit.

As the two cutters continue their outward movement, as a result of expansion of the spring and downward movement of the upper and intermediate thrust blocks, the intermediate block 5200 finally engages the lower thrust lock 5273, which is urged downwardly to swing the third cutter supporting member 22b and cutter [0b outwardly. Rotation of the drill bit is continued, the spring 50 shifting all three blocks downwardly together and urging the cutters outwardly, the first cutter continuing the formation of the shoulder by producing the outermost portion R of the latter. When the lower block 5217 engages the lower body guide sl, the cutters I0, [0a, [0b are precluded from swinging outwardly to any further extent, but they are then located with the outermost cutter It! disposed upon the outermost portion R of the shoulder, the intermediate cutter Iila on the intermediate portion S of the shoulder, and the innermost cutter [0b upon the innermost portion T of the shoulder. The annular paths R, S, T traced by the cutters upon the formation shoulder C during rotation of the bit preferably overlap one another to a slight extent; to insure that the cutter teeth will operate upon all portions of the formation shoulder.

After the formation shoulder has been produced, primarily by the outermost cutter I0, down weight or drilling weight may be imposed on the drilling string B, which will telescope the mandrel I2 in the body I I and shift the lower end I3a of the kelly I3 into engagement with the thrust washer 39, the drilling weight then being transmitted directly through the body I I to the cutter supporting members 22, 22a, 22b and the cutters I0, Illa, lob. During the imposition of the drilling weight, the bit is rotated at the proper speed, the cutters operating upon their individual annular portions of the shoulder to remove the formation material in a downward direction, effecting the hole enlarging to the desired greatly increased diameter. As mentioned above, the downward telescoping of the driving mandrel I2 in the body I I also locates the mandrel shoulder 30b immediately adjacent the upper thrust block 52, to prevent any substantial retraction of the cutters from their maximum expanded positions.

When the well bore has been enlarged to the desired length, or upon the cutters becoming dull, the entire tool may be removed from the well bore merely by elevating the drill string B. Such elevating movement will lift the driving mandrel I2 within the main bit body II and will raise the mandrel shoulder 3% above the upper thrust block 52. As the tool passes into an upper lesser diameter portion of the well bore, or into the well casing, the walls of the casing or well bore will engage the cutter supporting legs 22, 22a, 22b, and force them inwardly against the action of the i antiel' pring 56. The cutter supporting memresult of shift n the drivin mand l 2 w wardly Within the body i. to po i el fo th thrust block 52. 52a. 5 b downwardl and th cutter supporting legs and cutters outwardly in he above-noted sequenc in order to prod the formation shoulder C. The extent of d wnwar m vem nt of th mandrel l2, and of outwar expen ion of the cutters, is limited by engagement of the lower end [3a of the kelly i3 with the thrust and guide washer 39.

It is, accordingly, apparent that an expansible drill bit has been provided which is capable of increasing the well bore diameter considerably. A formation shoulder of substantially great lateral extent is first formed, and each cutter is caused to operate upon its individual portion of this shoulder; so that each cutter, in efiect, constitutes an individual bit capable of enlarging the well bore from one diameter to another diameter. Thus, the innermost cutter b will enlarge the hole by the radius T, the next, or intermediate, cutter iila will increase the size of the enlarged hole by the additional radius S, and the outer cutter I 0 will further increase the size of the hole by the additional radius R. The cutters, collectively, progressively increase the bore hole diameter, and achieve the same purpose as if individual bits were run in the hole, one bit increasing the well bore size by the radius T, another bit then being run in the hole to further increase the hole size by the radius S, and still another bit being thereafter run in the hole to further increase the size of the bore by the radius B. By virtue of the present invention, single bit achieves the same result as the plurality of bits, with a single run of the equipment in the bore hole. In addition, the ability to use roller cutters allows the bit to operate effectively in comparatively hard formations, and to increase the bore hole size in such formations considerably. The entire bit is comparatively simple and compact.

The inventor claims:

1. In an expansible drill bit: a body; a plurality of individual cutter means mounted on said body for lateral movement with respect to said body and circumferentially disposed around said body; one of said cutter means being shiftable laterally outward to a greater maximum extent than another of said cutter means to trace an annular cutting path outside the cuttin path traced by said another cutting means; means engageable with all of said individual cutter means for so shifting said individual cutter means laterally outward; elastic means acting on said shifting means for urging said shifting means in a direction to expand said cutter means laterally outward; and means engageable with said shifting means for preventing substantial retraction of all of said individual cutter means from their maximum expanded positions.

2. In an expensible drill bit: a body; a plurality of supporting members disposed circumferentially around said body; a cutter mounted on each of said supporting members; means mounting said supporting members on said body for lateral movement with respect to said body; means movable relatively to said body and operatively connected to said supporting members for shifting said supporting members and cutters 1'0 laterally of said body; the position of'the mounting means on said body, the position of each cutter on e h upp t g me and t po ts of operative connections of said shifting means to sa d su po t m m being s t a movement of said shifting means expands said cutters ,difierent maximum lateral distances from the axis of said body, in order that one of said cutters traces an annular cutting path inside of the cutting path traced by another of said outters; and means connectible to a drill string and slidably splined to said body and having means thereon engageable with said movable means for so shifting said supporting members and cutters.

3. In an expansible drill bit: a body; a plurality of supporting members disposed circumferentially around said body; a cutter mounted on each of said supporting members; means mounting said supporting members on said body for lateral movement with respect to said body; means movable relatively to said body and operativel nnected to said supporting members $01" shifting said supporting members and cutters laterally of said body; the position of the mountin means on said body, the position of each cutter on each supporting member and the points of operative connections or said shifting means to said supporting members being such that movement of said shifting means expands said cutters different maximum lateral distances from the axis of said body, in order that one Of said cutters traces an annular cutting path inside of the cutting path traced by another of said cutters; spring means engaging said movable mea s o s ift sa d ovable eans along said body; and means connectible to a drill string and slidably splined to said body and having an abutmerit thereon engageable with said spring means for preventing substantial retraction of said spring means, movable means and supporting members and of said cutters from their maximum outward expanded positions.

4. In an expansible drill bit: a body; a plurality of supporting members disposed circumferentially around said body; a cutter mounted on each of said supporting members; means mounting said supporting members on said body for lateral movement with respect to said body; means operatively engageable with a first supporting member for shifting said first supporting member laterally of said body; and means operatively engageable with a second supporting 'member for shifting said second supporting member laterally of said body after shifting of said first supporting member has commenced.

5. In an expansible drill bit: a body; a plurality of supporting members pivotally mounted on said body and disposed circumferentially around said body; a cutter mounted on each of said supporting members; a first link connected to a first of said supporting members; a second link connected to a second of said supporting members; the distance between the pivotal axis or" said second supporting member and the point of connection of said second link to said second supporting member being substantially different than the distance between the pivotal axis of said first supporting member and the point of connection of said first link to said first supporting member; and means operatively connected to said links for shiftin said links to expand said cutters laterally different distances from the axis of said body.

6. In an expansible drill bit: a body; a plurality of supporting members pivotally mounted on said body and disposed circumferentially around said body; a cutter mounted on each of said supporting members; a first link connected to a first of said supporting members; a second link connected to a second of said supporting members; the distance between the pivotal axis of said second supporting member and the point of connection of said second link to said second supporting member being substantially different than the distance between the pivotal axis of said first supporting member and the point of connection of said first link to said first supporting member; and means engaging said links and movable longitudinally alon said body to shift said links and supporting members and expand said cutters laterally different distances from the axis of said body.

'7. In an expansible drill bit: a body; a plurality of supporting members pivotally mounted on said body and disposed circumferentially around said body; a cutter mounted on each of said supporting members; a first link connected to a first of said supporting members; a second link connected to a second of said supporting members; the distance between the pivotal axis of said second supporting member and the point of connection of said second link to said second supporting member being substantially different than the distance between the pivotal axis of said first supporting member and the point of connection of said first link to said first supporting member; thrust means connected to said links; and means for shifting said thrust means longitudinally of said body to expand said cutters laterally different distances from the axis of said body.

8. In an expansible drill bit: a body; a plurality of supportin members pivotally mounted on said body and disposed circumferentially around said body; a cutter mounted on each of said supporting members; a first link connected to a first of said supporting members; a second link connected to a second of said supporting members; the distance between the pivotal axis of said second supporting member and the point of connection of said second link to said second supporting member being greater than the distance between the pivotal axis of said first supporting member and the point of connection of said first link to said first supporting member; a first thrust means connected to said first link; a second thrust means connected to said second link and initially spaced from said first thrust means; and means for shifting said first thrust means along said body into engagement with said second thrust means.

9. In an expansible drill bit: a body; a plurality of supporting members longitudinally mounted on said body and disposed circumferentially around said body; a cutter mounted on each of said supporting members; a first link connected to a first of said supporting members; a second link connected to a second of said supporting members; the distance between the pivotal axis of said second supporting member and the point of connection of said second link to said second supporting member being greater than the distance between the pivotal axis of said first supporting member and the point of connection of said first link to said first supporting member; a first thrust means connected to said rst link; a second thrust means connected to said second link and initially spaced from said first thrust means; means for shifting said first thrust means longitudinally of said body into engagement with said second thrust means and for then shifting both of said thrust means longitudinally of said body to expand said cutters laterally different distances from the axis of said body; stop means for limiting the extent of longitudinal movement of said thrust means along said body; and means connectible to a drill string for preventing substantial retraction of said supporting members and cutters from their maximum lateral outward positions.

10. In an expansible drill bit: a body; a plurality of supporting members pivotally mounted on said body and disposed circumferentially around said body; a cutter mounted on each of said supporting members; a first link connected to a first of said supporting members; a second link connected to a second of said supporting members; a first thrust means connected to said first link; a second thrust means connected to said second link and initially spaced from said first thrust means; and means for shifting said first thrust means along said body into engagement with said second thrust means and for then shifting both of said thrust means along said body.

11. In an expansible drill bit: a body; a plurality of supporting members pivotally mounted on said body and disposed circumferentially around said body; a cutter mounted on each of said supporting members; a first link connected to a first of said supporting members; a second link connected to a second of said supporting members; the distance between the pivotal axis of said second supporting member and the point of connection of said second link to said second supporting member being greater than the distance between the pivotal axis of said first supporting member and the point of connection of said first link to said first supporting member; a mandrel slidably splined to said body and adapted for connection to a drill string; a first thrust block on said mandrel connected to said first link; a second thrust block on said mandrel connected to said second link and initially spaced from said first thrust block; spring means engaging said first thrust block to shift said first thrust block along said mandrel into engagement with said second thrust block and to then shift both of said thrust blocks along said mandrel; and means on said mandrel engageable with said first thrust block for preventing substantial retraction of said cutters from their maximum outwardly expanded positions.

12. In an expansible drill bit: a body; three supporting members pivotally mounted on said body and disposed circumferentially around said body; a cutter mounted on each of said supporting members; a first link connected to a first of said supporting members; a second link connected to a second of said supporting members; a third link connected to a third of said supporting members; the distance between the pivotal axis of said third supporting member and the point of connection of said third link to said third supporting member being greater than the distance between the pivotal axis of said second supporting member and the point of connection of said second link to said second supporting member, the distance between the pivotal axis of said second supporting member and the point of connection of said second link to said second supporting member being greater than the distance between the pivotal axis of said first supporting member and the point of connection of said first link to said first supporting member;

a mandrel slidably splined to said body and adapted for connection to a drill string; an upper thrust block on said mandrel connected to said first link; an intermediate thrust block on said mandrel connected to said second link and disposed below and spaced initially from said first thrust block; a lower thrust block connected to said third link and disposed below and spaced initially from said second thrust block; a spring bearing upon said body and upper thrust block for urging all of said blocks downwardly alon said mandrel to expand said cutters laterally outward; and means on said mandrel engageable with said upper thrust block to prevent substantial retraction of said cutters from their maximum outwardly expanded positions.

13. In an expansible drill bit: a body; a plurality of individual cutter means mounted on said body for lateral movement with respect to said body; one of said cutter means being shiftable laterally outward to a greater maximum extent than another of said cutter means to trace an annular cutting path outside the cutting path traced by said another cutting means; means engageable with all of said individual cutter means for so shifting said individual cutter means laterally outward; and means connectible to a drill string and slidably splined to said body and having an abutment thereon engageable with said movable means for preventing substantial retraction of said movable means and of all of said individual cutter means from their maximum expanded positions.

14. In an expansible drill bit: a body; a plurality of supporting members disposed circumferentially around said body; a cutter mounted on each of said supporting members; means mounting said supporting members on said body for lateral movement with respect to said body; means movable relative to said body and operatively connected to said supporting members for shifting said supporting members and cutters laterally of said body; the position of the mounting means on said body, the position of each cutter on each supporting member and the points of operative connections of said shifting means to said supporting members being such that movement of said shifting means expands said cutters different maximum lateral distances from the axis of said body, in order that one of said cutters traces an annular cutting path inside of the cutting path traced by another of said outters; spring means engaging said body and said movable means to shift said movable means along said body; and means connectible to a drill string and slidably splined to said body and having an abutment thereon engageable with said spring means for preventing substantial retraction of said spring means, movable means and supporting members and of said cutters from their maximum outward expanded positions.

15. In an expansible drill bit: a body; a plurality of supporting members disposed circumferentially around said body; a cutter mounted on each of said supporting members; means mounting said supporting members on said body for lateral movement with respect to said body; means operatively engageable with a first supporting member for shifting said first supporting member laterally of said body; and means engaged by said first-mentioned shifting means and operatively engageable with a second supporting member for shifting said second supporting member laterally of said body after shift- 14 ing of said first supporting member has commenced.

16. In an expansible drill bit: a body; a plurality of supporting members mounted on said body for movement laterally of said body and disposed circumferentially around said body; a cutter mounted on each of said supporting members; a first thrust means; a second thrust means initially spaced from said first thrust means; means operatively connecting said first thrust means to a first of said supporting members; means operatively connecting said second thrust means to a second of said supporting members; and means for shifting said first thrust means along said body into engagement with said second thrust means.

17. In an expansible drill bit: a body; a plurality of supporting members mounted on said body for movement laterally of said body and disposed circumferentially around said body; a cutter mounted on each of said supporting members; a first link connected to a first of said supporting members; a second link connected to a second of said supporting members; a first thrust means connected to said first link; a second thrust means connected to said second link and initially spaced from said first thrust means; and means for shifting said first thrust means along said body into engagement with said second thrust means.

18. In an expansible drill bit: a body; a plurality of supporting members disposed circumferentially around said body; a cutter mounted on each of said supporting members; means mounting said supporting members on said body for lateral movement with respect to said body; means movable longitudinally of said body and operatively engageable with a first supporting member for shifting said first supporting member laterally of said body; means movable longitudinally of said body and relative to said firstmentioned means and operatively engageable with the second supporting member for shifting said second supporting member laterally of said body.

19. In an expansible drill bit: a body; a plu rality of supporting members pivotally mounted on said body and disposed circumferentially around said body; a cutter mounted on each of said supporting members; a first means engaging a first of said supporting members; a second means engaging a second of said supporting members; the distance between the pivotal axis of said second supporting member and the point of engagement of said second means with said second supporting member being substantially different than the distance between the pivotal axis of said first supporting member and the point of engagement of said first means with said first supporting member; and means operatively connected to said first and second means for shifting said first and second means to expand said cutters laterally difierent distances from the axis of said body.

ARCHER W. KAMMERER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,667,155 Higdon Apr. 24, 1928 2,169,502 Santiago Aug. 15, 1939 2,173,018 Hurley Sept. 12, 1939 2,330,083 Sewell Sept. 21, 1943 2,457,628 Baker Dec. 28, 1948 2,466,991 Kammerer Apr. 12, 1949 

